It benefits landlords.
I don't know enough about economics these days to know if anyone who knows a lot about thus stuff thinks this is true, but it seems on the face of it to be absurd, since it would mean that pay raises are substantially diminished by rents paid for anything where demand is not elastic. I mean, I'm not insisting that cannot possibly be true, but it seems unlikely ...
The relevance of this is amplified by the fact that land is a required input for all forms of production. People and machines must exist in space, and therefore demand land.
This does not apply to any other asset that we care about.
The housing:land demand ratio is also not fixed, due to multi-level dwellings (hence, for example, Singapore or Hong Kong), or increased density (e.g. ADUs or smaller lots).
I just don't see why you see UBI only affecting owners of a nearly-inelastic resource (land) rather than everything else too (even if to a lesser degree) ?